Sequential Circuits Pro One w/ MTG Turbo CPU+MIDI Mod

This Pro-One is fully functional and in very good condition.  Aside from the wood end panels being slightly different colors from one another, this is a very clean Pro-One.  This Pro-One has been modded by Switched On to include the MTG Pro-One Turbo CPU+MIDI. 

Turbo CPU

The MTG Pro One Turbo replacement CPU Module is a drop-in replacement microcontroller for the Sequential Circuits Pro One's 8021 CPU (AKA P8021/8021H/P8021H).


  • Each sequence can be up to 256 steps (compared to total of 40 steps on the original).
  • Sequences are retained in memory even after power-down. The CPU module does not use a battery.
  • Power-on settable parameters for clock start mode, arpeggio up/down end notes, arpeggio down mode and arpeggio gate time.
  • Sequence Tie mode allows for a variety of note lengths.
  • Sequence End mode lets you chain the two sequences.
 Turbo MIDI

The above plus a MIDI In/Out interface board that adds the following features:

  • Firmware update (“re-flashing”) over MIDI (using MIDIOX or similar).
  • Settable MIDI channel.
  • Receive MIDI note data.
  • Monophonic MIDI output of arpeggiator and sequencer data.
  • Polyphonic MIDI output of keyboard data.
  • Arpeggiator and sequencer sync-able to MIDI Sync In (settable clock rate).
  • Load/Save sequence data over MIDI.
  • MIDI In, MIDI Out and optional MIDI Thru.

One of the more beastly of mono synths ever created, the Sequential Circuits Pro-One is a powerhouse of punchy bass and singing leads. It is comparable with the Roland SH-101 or the Moog Source, feature-wise, but sounds very different from either. The oscillator hard-sync sounds are especially exciting.

  • CEM 3340 Oscillators x 2
  • CEM 3340 Lowpass filter
  • Oscillator Hard Sync
  • Modulation Matrix 
  • Arpeggiator and Sequencer
  • CV+Gate Control for the Oscillators/Audio In/CV Filter Control

Switched On has acquired a sterling reputation for its careful and professional shipping and handling.  Allow up to 3 business days for packing and handling.  All used items are 100% functional and warrantied against electronic failure up to 30 days after delivery unless otherwise noted.